adam@mtund.UUCP (01/25/87)
John Cugini: >> .... to explain, or at least discuss, private >> subjective events. If it be objected that the latter are outside the >> proper realm of science, so be it, call it schmience or philosophy or >> whatever you like. - but surely anything that is REAL, even if >> subjective, can be the proper object for some sort of rational >> study, no? Stevan Harnad: > Some sort, no doubt. But not an objective sort, and that's the point. > Empirical psychology, neuroscience and artificial intelligence are > all, I presume, branches of objective inquiry. > .... Let's leave the subjective discussion of private events > to lit-crit, where it belongs. Stevan Harnad makes an unstated assumption here, namely, that subjective variables are not amenable to objective measurement. But if by "objective" Steve means, as I think he does, "observer-invariant", than this assumption is demonstrably false. I shall proceed to demonstrate this in two parts: (1) private events are amenable to parametric measurement; and (2) relevant results of such measurement can be observer-invariant. (1) Whether or not a stimulus is experienced as belonging to some target category is clearly a private event. Now data for the measurement of d', the detection-theoretic measure of discriminability, are usually gathered using overt behavior, such as pressing "target" and "non-target" buttons. But in principle, d' can be measured without any resort to externally observable behavior. Suppose I program a computer to present a sequence of stimuli and, following enough time after each stimulus to allow the observer to mentally classify the experience as target or non-target, display the actual category of the preceding stimulus. The observer would use this information to maintain a mental count of hits and false alarms. The category feedback for the last stimulus could be followed by a display of a table for the conversion of hit and false alarm rates into d'. Thus, the observer would be able to mentally compute d' without engaging in any externally observable behavior whatever. (2) In some well-defined contexts, the variation of d' with an independent variable is as lawful as anything in the "known to be objective" sciences such as physics (see Reed, Memory and Cognition 1976, 4(4), 453-458, equation 5 and bottom panel of figure 1, for an example of this). The parameters of such lawful relationships will differ from observer to observer, but their form is observer-invariant. In principle, two investigators could perform the experiment as in (1) above, and obtain objective (in the sense of observer-independent) results as to the form of the resulting lawful relationships between, for example, d' and memory retention time, *without engaging in any externally observable behavior until it came time to compare results*. The following analogy (proposed, if I remember correctly, by Robert Efron) may illuminate what is happening here. Two physicists, A and B, live in countries with closed borders, so that they may never visit each other's laboratories and personally observe each other's experiments. Relative to each other's personal perception, their experiments are as private as the conscious experiences of different observers. But, by replicating each other's experiments in their respective laboratories, they are capable of arriving at objective knowledge. This is also true, I submit, of the psychological study of private, "subjective" experience. Adam Reed mtund!adam,attmail!adamreed
harnad@mind.UUCP (01/27/87)
adam@mtund.UUCP (Adam V. Reed), of AT&T ISL Middletown NJ USA, wrote: > Stevan Harnad makes an unstated assumption... that subjective > variables are not amenable to objective measurement. But if by > "objective" Steve means, as I think he does, "observer-invariant", then > this assumption is demonstrably false. I do make the assumption (let me state it boldly) that subjective variables are not objectively measurable (nor are they objectively explainable) and that that's the mind/body problem. I don't know what "observer-invariant" means, but if it means the same thing as in physics -- which is that the very same physical phenomenon can occur independently of any particular observation, and can in principle be measured by any observer, then individuals' private events certainly are not such, since the only eligible observer is the subject of the experience himself (and without an observer there is no experience -- I'll return to this below). I can't observe yours and you can't observe mine. That's one of the definitive features of the subjective/objective distinction itself, and it's intimately related to the nature of experience, i.e., of subjectivity, of consciousness. > Whether or not a stimulus is experienced as belonging to some target > category is clearly a private event...[This is followed by an > interesting thought-experiment in which the signal detection parameter > d' could be calculated for himself by a subject after an appropriate > series of trials with feedback and no overt response.]... the observer > would be able to mentally compute d' without engaging in any externally > observable behavior whatever. Unfortunately, this in no way refutes the claim that subjective experience cannot be objectively measured or explained. Not only is there (1) no way of objectively testing whether the subject's covert calculations on that series of trials were correct, not only is there (2) no way of getting any data AT ALL without his overt mega-response at the end (unless, of course, the subject is the experimenter, which makes the whole exercise solipsistic), but, worst of all, (3) the very same performance data could be generated by presenting inputs to a computer's transducer, and no matter how accurately it reported its d', we presumably wouldn't want to conclude that it had experienced anything at all. So what's OBJECTIVELY different about the human case? At best, what's being objectively measured happens to correlate reliably with subjective experience (as we can each confirm in our own cases only -- privately and subjectively). What we are actually measuring objectively is merely behavior (and, if we know what to look for, also its neural substrate). By the usual objective techniques of scientific inference on these data we can then go on to formulate (again objective) hypotheses about underlying functional (causal) mechanisms. These should be testable and may even be valid (all likewise objectively). But the testability and validity of these hypotheses will always be objectively independent of any experiential correlations (i.e., the presence or absence of consciousness). To put it my standard stark way: The psychophysics of a conscious organism (or device) will always be objectively identical to that of a turing-indistinguishable unconscious organism (or device) that merely BEHAVES EXACTLY AS IF it were conscious. (It is irrelevant whether there are or could be such organisms or devices; what's at issue here is objectivity. Moreover, the "reliability" of the correlations is of course objectively untestable.) This leaves subjective experience a mere "nomological dangler" (as the old identity theorists used to call it) in a lawful psychophysical account. We each (presumably) know it's there from our respective subjective observations. But, objectively speaking, psychophysics is only the study of, say, the detecting and discriminating capacity (i.e., behavior) of our trandsucer systems, NOT the qualities of our conscious experience, no matter how tight the subjective correlation. That's no limit on psychophysics. We can do it as if it were the study of our conscious experience, and the correlations may all be real, even causal. But the mind/body problem and the problem of objective measurement and explanation remain completely untouched by our findings, both in practise and in principle. So even in psychophysics, the appropriate research strategy seems to be methodological epiphenomenalism. If you disagree, answer this: What MORE is added to our empirical mission in doing psychophysics if we insist that we are not "merely" trying to account for the underlying regularities and causal mechanisms of detection, discrimination, categorization (etc.) PERFORMANCE, but of the qualitative experience accompanying and "mediating" it? How would someone who wanted to undertake the latter rather than merely the former go about things any differently, and how would his methods and findings differ (apart from being embellished with a subjective interpretation)? Would there be any OBJECTIVE difference? I have no lack of respect for psychophysics, and what it can tell us about the functional basis of categorization. (I've just edited and contributed to a book on it.) But I have no illusions about its being in any better a position to make objective inroads on the mind/body problem than neuroscience, cognitive psychology, artificial intelligence or evolutionary biology -- and they're in no position at all. > In principle, two investigators could perform the [above] experiment > ...and obtain objective (in the sense of observer-independent) > results as to the form of the resulting lawful relationships between, > for example, d' and memory retention time, *without engaging in any > externally observable behavior until it came time to compare results*. I'd be interested in knowing how, if I were one of the experimenters and Adam Reed were the other, he could get "objective (observer-independent) results" on my experience and I on his. Of course, if we make some (question-begging) assumptions about the fact that the experience of our respective alter egos (a) exists, (b) is similar to our own, and (c) is veridically reflected by the "form" of the overt outcome of our respective covert calculations, then we'd have some agreement, but I'd hardly dare to say we had objectivity. (What, by the way, is the difference in principle between overt behavior on every trial and overt behavior after a complex-series-of-trials? Whether I'm detecting individual signals or calculating cumulating d's or even more complex psychophysical functions, I'm just an organism/device that's behaving in a certain way under certain conditions. And you're just a theorist making inferences about the regularities underlying my performance. Where does "experience" come into it, objectively speaking? -- And you're surely not suggesting that psychophyics be practiced as a solipsistic science, each experimenter serving as his own sole subject: for from solipsistic methods you can only arrive at solipsistic conclusions, trivially observer-invariant, but hardly objective.) > The following analogy (proposed, if I remember correctly, by Robert > Efron) may illuminate what is happening here. Two physicists, A and B, > live in countries with closed borders, so that they may never visit each > other's laboratories and personally observe each other's experiments. > Relative to each other's personal perception, their experiments are > as private as the conscious experiences of different observers. But, by > replicating each other's experiments in their respective laboratories, > they are capable of arriving at objective knowledge. This is also true, > I submit, of the psychological study of private, "subjective" > experience. As far as I can see, Efron's analogy casts no light at all. It merely reminds us that even normal objectivity in science (intersubjective repeatability) happens to be piggy-backing on the existence of subjective experience. We are not, after all, unconscious automata. When we perform an "observation," it is not ONLY objective, in the sense that anyone in principle can perform the same observation and arrive at the same result. There is also something it is "like" to observe something -- observations are also conscious experiences. But apart from some voodoo in certain quantum mechanical meta-theories, the subjective aspect of objective observations in physics seems to be nothing but an innocent fellow-traveller: The outcome of the Michelson-Morley Experiment would presumably be the same if it were performed by an unconscious automaton, or even if WE were unconscious automata. This is decidely NOT true of the (untouched) subjective aspect of a psychophysical experiment. Observer-independent "experience" is a contradiction in terms. (Most scientists, by the way, do not construe repeatability to require travelling directly to one another's labs; rather, it's a matter of recreating the same objective conditions. Unfortunately, this does not generalize to the replication of anyone else's private events, or even to the EXISTENCE of any private events other than one's own.) Note that I am not denying that objective knowledge can be derived from psychophysics; I'm only denying that this can amount to objective knowledge about anything MORE than psychophysical performance and its underlying causal substrate. The accompanying subjective phenomenology is simply not part of the objective story science can tell, no matter how, and how tightly, it happens to be coupled to it in reality. That's the mind/body problem, and a fundamental limit on objective inquiry. Methodological epiphenomenalism recommends we face it and live with it, since not that much is lost. The "incompleteness" of an objective account is, after all, just a subjective problem. But supposing away the incompleteness -- by wishful thinking, hopeful over-interpretation, hidden (subjective) premises or blurring of the objective/subjective distinction -- is a logical problem. -- Stevan Harnad (609) - 921 7771 {allegra, bellcore, seismo, rutgers, packard} !princeton!mind!harnad harnad%mind@princeton.csnet
adam@mtund.UUCP (02/01/87)
This is a reply to Stevan Harnad, who wrote: > adam@mtund.UUCP (Adam V. Reed), of AT&T ISL Middletown NJ USA, wrote: > > > Stevan Harnad makes an unstated assumption... that subjective > > variables are not amenable to objective measurement. But if by > > "objective" Steve means, as I think he does, "observer-invariant", then > > this assumption is demonstrably false. > > I do make the assumption (let me state it boldly) that subjective > variables are not objectively measurable (nor are they objectively > explainable) and that that's the mind/body problem. I don't know what > "observer-invariant" means, but if it means the same thing as in > physics -- which is that the very same physical phenomenon can > occur independently of any particular observation, and can in > principle be measured by any observer, then individuals' private events > certainly are not such, since the only eligible observer is the > subject of the experience himself (and without an observer there is no > experience -- I'll return to this below). I can't observe yours and you > can't observe mine. Yes, and in Efron's analogy, A can't observe B's, and vice versa. However, I don't buy the assumption that two must *observe the same instance of a phenomenon* in order to perform an *observer-independent measurement of the same (generic) phenomenon*. The two physicists can agree that they are studying the same generic phenomenon because they know they are doing similar things to similar equipment, and getting similar results. But there is nothing to prevent two psychologists from doing similar (mental) things to similar (mental) equipment and getting similar results, even if neither engages in any overt behavior apart from reporting the results of his measurements to the other. My point is that this constitutes objective (observer-independent) measurement of private (no behavior observable by others) mental processes. > That's one of the definitive features of the > subjective/objective distinction itself, and it's intimately related to > the nature of experience, i.e., of subjectivity, of consciousness. > > > Whether or not a stimulus is experienced as belonging to some target > > category is clearly a private event...[This is followed by an > > interesting thought-experiment in which the signal detection parameter > > d' could be calculated for himself by a subject after an appropriate > > series of trials with feedback and no overt response.]... the observer > > would be able to mentally compute d' without engaging in any externally > > observable behavior whatever. > > Unfortunately, this in no way refutes the claim that subjective experience > cannot be objectively measured or explained. Not only is there (1) no way > of objectively testing whether the subject's covert calculations on > that series of trials were correct, This objection applies with equal force to the observation, recording and calculations of externally observable behavior. So what? > not only is there (2) no way of > getting any data AT ALL without his overt mega-response at the end Yes, but *this is not what is being measured*. Or is the subject matter of physics the communication behavior of physicists? > (unless, of course, the subject is the experimenter, which makes the > whole exercise solipsistic), but, worst of all, (3) the very same > performance data could be generated by presenting inputs to a > computer's transducer, and no matter how accurately it reported its > d', we presumably wouldn't want to conclude that it had experienced anything > at all. So what's OBJECTIVELY different about the human case? What is objectively different about the human case is that not only is the other human doing similar (mental) things, he or she is doing those things to similar (human mind implemented on a human brain) equipment. If we obtain similar results, Occam's razor suggests that we explain them similarly: if my results come from measurement of subjectively experienced events, it is reasonable for me to suppose that another human's similar results come from the same source. But a computer's "mental" equipment is (at this point in time) sufficiently dissimilar from a human's that the above reasoning would break down at the point of "doing similar things to similar equipment with similar results", even if the procedures and results somehow did turn out to be identical. > At best, what's being objectively measured happens to correlate > reliably with subjective experience (as we can each confirm in our own > cases only -- privately and subjectively). What we are actually measuring > objectively is merely behavior Not true. As I have shown in my original posting, d' can be measured without there *being* any behavior prior to measurement. There is nothing in Harnad's reply to refute this. > (and, if we know what to look for, also > its neural substrate). By the usual objective techniques of scientific > inference on these data we can then go on to formulate (again objective) > hypotheses about underlying functional (causal) mechanisms. These should > be testable and may even be valid (all likewise objectively). But the > testability and validity of these hypotheses will always be objectively > independent of any experiential correlations (i.e., the presence or > absence of consciousness). Why? And how can this be true in cases when it is the conscious experience that is being measured? > To put it my standard stark way: The psychophysics of a conscious > organism (or device) will always be objectively identical to that > of a turing-indistinguishable unconscious organism (or device) that > merely BEHAVES EXACTLY AS IF it were conscious. (It is irrelevant whether > there are or could be such organisms or devices; what's at issue here is > objectivity. Moreover, the "reliability" of the correlations is of > course objectively untestable.) This leaves subjective experience a > mere "nomological dangler" (as the old identity theorists used to call > it) in a lawful psychophysical account. We each (presumably) know it's > there from our respective subjective observations. But, objectively speaking, > psychophysics is only the study of, say, the detecting and discriminating > capacity (i.e., behavior) of our trandsucer systems, NOT the qualities of our > conscious experience, no matter how tight the subjective correlation. > That's no limit on psychophysics. We can do it as if it were the study > of our conscious experience, and the correlations may all be real, > even causal. But the mind/body problem and the problem of objective > measurement and explanation remain completely untouched by our findings, > both in practise and in principle. The above re-states Steve's position, but fails deal with my objections to it. > So even in psychophysics, the appropriate research strategy seems to > be methodological epiphenomenalism. If you disagree, answer this: What > MORE is added to our empirical mission in doing psychophysics if we > insist that we are not "merely" trying to account for the underlying > regularities and causal mechanisms of detection, discrimination, > categorization (etc.) PERFORMANCE, but of the qualitative experience > accompanying and "mediating" it? How would someone who wanted to > undertake the latter rather than merely the former go about things any > differently, and how would his methods and findings differ (apart from > being embellished with a subjective interpretation)? Would there be any > OBJECTIVE difference? I think so - I would not accept as legitimate any psychological theory which appeared to contradict my conscious experience, and failed to account for the apparent contradiction. As far as I can tell, Steve's position means that he would not disqualify a psychological theory just because it happened to be contradicted by his own conscious experience. > I have no lack of respect for psychophysics, and what it can tell us > about the functional basis of categorization. (I've just edited and > contributed to a book on it.) But I have no illusions about its being > in any better a position to make objective inroads on the mind/body > problem than neuroscience, cognitive psychology, artificial > intelligence or evolutionary biology -- and they're in no position at all. > > In principle, two investigators could perform the [above] experiment > > ...and obtain objective (in the sense of observer-independent) > > results as to the form of the resulting lawful relationships between, > > for example, d' and memory retention time, *without engaging in any > > externally observable behavior until it came time to compare results*. > > I'd be interested in knowing how, if I were one of the experimenters > and Adam Reed were the other, he could get "objective > (observer-independent) results" on my experience and I on his. Of > course, if we make some (question-begging) assumptions about the fact > that the experience of our respective alter egos (a) exists, (b) is > similar to our own, and (c) is veridically reflected by the "form" of the > overt outcome of our respective covert calculations, then we'd have some > agreement, but I'd hardly dare to say we had objectivity. These assumptions are not "question-begging": they are logically necessary consequences of applying Occam's razor to this situation (see above). And yes, I would tend to regard the resulting agreement among different subjective observers as evidence for the objectivity of their measurements. > (What, by the way, is the difference in principle between overt behavior > on every trial and overt behavior after a complex-series-of-trials? > Whether I'm detecting individual signals or calculating cumulating d's > or even more complex psychophysical functions, I'm just an > organism/device that's behaving in a certain way under certain > conditions. And you're just a theorist making inferences about the > regularities underlying my performance. Where does "experience" come > into it, objectively speaking? -- And you're surely not suggesting that > psychophyics be practiced as a solipsistic science, each experimenter > serving as his own sole subject: for from solipsistic methods you can > only arrive at solipsistic conclusions, trivially observer-invariant, > but hardly objective.) For measurement to be *measurement of behavior*, the behavior must be, in the temporal sequence, prior to measurement. But if the only overt behavior is the communication of the results of measurement, then the behavior occurs only after measurement has already taken place. So the measurement in question cannot be a measurement of behavior, and must be a measurement of something else. And the only plausible candidate for that "something else" is conscious experience. > > The following analogy (proposed, if I remember correctly, by Robert > > Efron) may illuminate what is happening here. Two physicists, A and B, > > live in countries with closed borders, so that they may never visit each > > other's laboratories and personally observe each other's experiments. > > Relative to each other's personal perception, their experiments are > > as private as the conscious experiences of different observers. But, by > > replicating each other's experiments in their respective laboratories, > > they are capable of arriving at objective knowledge. This is also true, > > I submit, of the psychological study of private, "subjective" > > experience. > > As far as I can see, Efron's analogy casts no light at all. See my comments at the beginning of this reply. > It merely reminds us that even normal objectivity in science (intersubjective > repeatability) happens to be piggy-backing on the existence of > subjective experience. We are not, after all, unconscious automata. When we > perform an "observation," it is not ONLY objective, in the sense that > anyone in principle can perform the same observation and arrive at the > same result. There is also something it is "like" to observe > something -- observations are also conscious experiences. > > But apart from some voodoo in certain quantum mechanical meta-theories, > the subjective aspect of objective observations in physics seems to be > nothing but an innocent fellow-traveller: The outcome of the > Michelson-Morley Experiment would presumably be the same if it were > performed by an unconscious automaton, or even if WE were unconscious automata. > This is decidely NOT true of the (untouched) subjective aspect of a > psychophysical experiment. Observer-independent "experience" is a > contradiction in terms. Yes, but observer-independent *measurement of* experience is not. See above. > (Most scientists, by the way, do not construe repeatability to require > travelling directly to one another's labs; rather, it's a matter of > recreating the same objective conditions. Unfortunately, this does not > generalize to the replication of anyone else's private events, or even > to the EXISTENCE of any private events other than one's own.) Yes it does: see the argument from Occam's razor earlier in this article. > Note that I am not denying that objective knowledge can be derived > from psychophysics; I'm only denying that this can amount to objective > knowledge about anything MORE than psychophysical performance and its > underlying causal substrate. The accompanying subjective phenomenology is > simply not part of the objective story science can tell, no matter how, and > how tightly, it happens to be coupled to it in reality. That's the > mind/body problem, and a fundamental limit on objective inquiry. Steve seems to be saying that the mind-body problem constitutes "a fundamental limit on objective inquiry", i.e. that this problem is *in principle* incapable of ever being solved. I happen to think that human consciousness is a fact of reality and, like all facts of reality, will prove amenable to scientific explanation. And I like to think that this explanation will constitute, in some scientifically relevant sense, a solution to the "mind-body problem". So I don't see this problem as a "fundamental limit". > Methodological epiphenomenalism recommends we face it and live with > it, since not that much is lost. The "incompleteness" of an objective > account is, after all, just a subjective problem. But supposing away > the incompleteness -- by wishful thinking, hopeful over-interpretation, > hidden (subjective) premises or blurring of the objective/subjective > distinction -- is a logical problem. Yes, but need it remain one forever? Adam Reed (mtund!adam, attmail!adamreed)